(1) Field of the Invention
This invention relates to static neutralizers, and more particularly relates to corona discharge devices in which one side of an A.C. high voltage power source is connected to a discharge electrode, usually of pointed disposition, and the other side connected to a conductive member or apertured casing adjacently spaced with respect to the discharge electrode to effect emission of ions of both polarities in the gap therebetween. This invention is especially concerned with static eliminators of the "shockless" type wherein the discharge electrodes are capacitively coupled, either indivdually or in groups, to the high voltage source in order to limit the short circuit current which can be drawn from a point so that the extent of arcing or electrical shock can be minimized. The present invention is specifically adapted to be used as an extended range static eliminator for impinging a stream of ionized air over considerable distances upon light sensitive articles to be neutralized.
(2) Prior Art
As is well known, static eliminators are devices for producing both positive and negative ions for the neutralization of articles which have been charged to a particular polarity, usually as a result of electrostatic, frictional, electrical or other created forces. When an A.C. high voltage of fairly high magnitude is applied across the discharge points and the grounded casing of such static bars, ions of each polarity are emitted. In a direct connected bar, such as shown in U.S. Pat. No. 3,137,806 or U.S. Pat. No. 3,156,847 (Air Gun), the discharge electrodes are coupled directly to the output of the A.C. high voltage while in a capacitively coupled static bar, such as shown in U.S. Pat. No. 3,120,626 or U.S. Pat. No. 3,179,849 (Air Gun), a capacitance is included between the discharge points and the power source in order to limit the short circuit current that can be drawn from a point, thereby minimizing arcing or shock. In either case, it can be observed that a breeze or stream of air is produced in the same direction as the points by virtue of the high voltage field created between the points, the electrode bases upon which the points are mounted and the ground electrode or casing mounted adjacent the sharp ends of the points. Usually where an extended range ionization is desired, an air stream is blown across the points in the same direction they are facing so that the ion breeze will be reinforced by the air stream. See U.S. Pat. No. 4,092,543. However, in the instance where the ion emission must be directed toward light sensitive articles, such as film or plates with photographic emulsions, it is necessary to shield the articles from corona glow developed around the points because such radiation would expose the film or emulsion prematurely.
If the static bars are entirely enclosed within a blower housing to block off the corona radiation from the sight of the articles, it has been found that the useful dual ion emission is dissipated within the housing long before the ions can emerge therefrom for impingement upon the articles themselves. In the development of the present invention, it was proposed to have the points of the discharge electrodes positioned adjacent the grounded blower housing and oriented in a direction opposite to that of the blower's air stream. An open bar construction was opted for because of the belief that the partially encircling casing of the conventional static bar construction would cup the flow of air and hence interfere with pattern of the blown air stream. However, it was found that in an open bar construction the air stream could neither overcome the ion breeze nor the high voltage field created about the bar bases upon which the points were mounted.
The present invention contemplates the use of a tubular casing, similar in many respects to the conventional grounded housing employed in the past for supporting the static bars, to act as both a shield for blocking the view of corona discharge emitted from the points (i.e. by orienting said points opposite to the direction of the blower air stream), and also as a shield about the high voltage bar assemble supporting the points themselves, thereby enabling ions emitted from the points to be carried along by the blown air stream per se.